Dielectric ceramic composition and ceramic capacitor

ABSTRACT

In a dielectric ceramic composition comprising: 100 mol % of an oxide of Ba, Ti and Zr; 0.25 to 1.5 mol % of an oxide of Re, Re representing one or more elements selected from the group consisting of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Y; 0.1 to 0.4 mol % of an oxide of Mg; and 0.03 to 0.6 mol % of oxides of one or more elements selected from the group consisting of Mn, V and Cr, the content of the oxide of the Ba, Ti and Zr is calculated by assuming that the oxide thereof is Ba(Ti 1−x Zr x )O 3 ; the contents of the oxides of the Re and Mg being calculated by assuming that the oxides thereof are Re 2 O 3  and MgO, respectively; the contents of the oxides of the Mn, V and Cr being calculated by assuming that the oxides thereof are Mn 2 O 3 , V 2 O 5  and Cr 2 O 3 , respectively. A ratio of Ba/(Ti 1−x Zr x ) ranges from about 1.000 to about 1.010 and x in Ti 1−x Zr x  ranges from about 0.05 to about 0.26.

FIELD OF THE INVENTION

The present invention relates to a ceramic capacitor and ceramic compositions therefor; and, more particularly, to reduction resistive dielectric ceramic compositions suitable for use as a dielectric layer of a ceramic capacitor having internal electrodes made of a base metal such as Ni and a ceramic capacitor fabricated by employing such ceramic compositions as a dielectric layer thereof.

BACKGROUND OF THE INVENTION

Recently, a base metal, e.g., Ni, is widely used in forming internal electrodes of multilayer ceramic capacitors for the purpose of reducing manufacturing costs. In case the internal electrodes are composed of the base metal, it is required that chip-shaped laminated bodies including therein the internal electrodes be sintered in a reductive atmosphere in order to prevent an oxidization of the internal electrodes. Accordingly, a variety of reduction resistive dielectric ceramic compositions have been developed.

Recent trend towards ever more miniaturized and dense electric circuits intensifies a demand for a further scaled down multilayer ceramic capacitor with higher capacitance. Keeping up with such demand, there has been made an effort to fabricate thinner dielectric layers and to stack a greater number of the thus produced dielectric layers.

However, when the dielectric layers are thinned out, a voltage applied to a unit thickness intrinsically increases. Accordingly, the operating life of the dielectric layers is shortened and thus a reliability of the multilayer ceramic capacitor is also deteriorated.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide highly reliable dielectric ceramic compositions and ceramic capacitors prepared by employing such dielectric ceramic compositions in forming dielectric layers thereof, wherein the dielectric ceramic compositions exhibit such electrical characteristics as a dielectric constant equal to or greater than 10,000, a capacitance variation of −80% to +30% (based on a capacitance obtained at a temperature of +25° C.) in the temperature range from −55° C. to +125° C., a dielectric loss “tan δ” of 10.0% or less and an accelerated life of 200,000 seconds or greater.

In accordance with a preferred embodiment of the present invention, there is provided a dielectric ceramic composition comprising: 100 mol part of an oxide of Ba, Ti and Zr, the content of the oxide of the Ba, Ti and Zr being calculated by assuming that the oxide thereof is Ba(Ti_(1−x)Zr_(x))O₃; 0.25 to 1.5 mol part of an oxide of Re, Re representing one or more elements selected from the group consisting of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Y, the content of the oxide of the Re being calculated by assuming that the oxide thereof is Re₂O₃; 0.1 to 0.4 mol part of an oxide of Mg, the content of the oxide of the Mg being calculated by assuming that the oxide thereof is MgO; and 0.03 to 0.6 mol part of oxides of one or more elements selected from the group consisting of Mn, V and Cr, the contents of the oxides of the Mn, V and Cr being calculated by assuming that the oxides thereof are Mn₂O₃, V₂O₅ and Cr₂O₃, respectively, wherein a ratio of Ba/(Ti_(1−x)Zr_(x)) ranges from about 1.000 to about 1.010 and x in Ti_(1−x)Zr_(x)) ranges from about 0.05 to about 0.26.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become apparent from the following description of a preferred embodiment given in conjunction with the accompanying drawing:

Drawing represents a schematic cross sectional view illustrating a multilayer ceramic capacitor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Compound powders of BaTiO₃, ZrO₂, BaCO₃, Re₂O₃, MgO, MnO₂, V₂O₅, Cr₂O₃, Fe₂O₃ and WO₃ were weighed in amounts as specified in the accompanying Tables 1-1 to 1-7 and mixed for about 20 hours by a wet method in a ball mill containing therein PSZ (partially sterilized zirconia) balls and water to thereby obtain a ceramic slurry. The produced ceramic slurry (containing 30% of water) was dehydrated and then dried by being heated at about 150° C. for 6 hours. It should be noted that “Re” is selected, e.g., from the group consisting of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Y.

TABLE 1 Dielectric Composition (mol %) Rare Earth Sample (Re₂O₃ Total Ba/ No. Element Content MgO Mn₂O₃ V₂O₅ Cr₂O₃ Content MoO₃ Ba Ti Zr (TiZr)  1 Ho 0.75 0.2 0.02 — — 0.02 0.05 100.3 86 14 1.003  2 Ho 0.75 0.2 — 0.02 — 0.02 0.05 100.3 86 14 1.003  3 Ho 0.75 0.2 — — 0.02 0.02 0.05 100.3 86 14 1.003  4 Ho 0.75 0.2 0.03 — — 0.03 0.05 100.3 86 14 1.003  5 Ho 0.75 0.2 — 0.03 — 0.03 0.05 100.3 86 14 1.003  6 Ho 0.75 0.2 — — 0.03 0.03 0.05 100.3 86 14 1.003  7 Ho 0.75 0.2 0.01 0.02 — 0.03 0.05 100.3 86 14 1.003  8 Ho 0.75 0.2 0.05 0.02 — 0.07 0.05 100.3 86 14 1.003  9 Ho 0.75 0.2 0.05 — 0.2 0.25 0.05 100.3 86 14 1.003  10 Ho 0.75 0.2 0.05 0.01 0.2 0.26 0.05 100.3 86 14 1.003  11 Ho 0.75 0.2 0.05 0.05 0.2 0.3 0.05 100.3 86 14 1.003  12 Ho 0.75 0.2 0.2 0.2 0.2 0.6 0.05 100.3 86 14 1.003  13 Ho 0.75 0.2 0.6 — — 0.6 0.05 100.3 86 14 1.003  14 Ho 0.75 0.2 — 0.6 — 0.6 0.05 100.3 86 14 1.003  15 Ho 0.75 0.2 — — 0.6 0.6 0.05 100.3 86 14 1.003  16 Ho 0.75 0.2 0.7 — — 0.7 0.05 100.3 86 14 1.003  17 Ho 0.75 0.2 — 0.7 — 0.7 0.05 100.3 86 14 1.003  18 Ho 0.75 0.2 — — 0.7 0.7 0.05 100.3 86 14 1.003  19 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0 100.3 86 14 1.003  20 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.025 100.3 86 14 1.003  21 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.05 100.3 86 14 1.003  22 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.1 100.3 86 14 1.003  23 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.2 100.3 86 14 1.003  24 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.3 100.3 86 14 1.003  25 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.4 100.3 86 14 1.003  26 Ho 0.75 0.2 0.025 0.05 0.2 0.275 0.05 100.3 86 14 1.003  27 Ho 0.00 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  28 Ho 0.25 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  29 Ho 0.5 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  30 Ho 1.0 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  31 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  32 Ho 2.0 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  33 Ho 4.0 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  34 Sm 0.25 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  35 Sm 0.75 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  36 Eu 0.75 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  37 Gd 0.75 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  38 Tb 0.75 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  39 Dy 0.75 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  40 Er 0.75 0.1 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  41 Tm 0.75 0.1 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  42 Yb 0.75 0.1 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  43 Yb 1.0 0.1 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  44 Y 1.0 0.1 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  45 Ho/ 0.5/ 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003   Dy 0.5  46 Ho/ 0.5/ 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 Dy/ 0.5/ Yb 0.5  47 Sm/ 0.2/ 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 Ho/ 0.5/ Yb 0.1  48 Sm/ 0.5 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 Yb 1.0  49 Ho 0.75 0 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  50 Ho 0.75 0.1 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  51 Ho 0.75 0.4 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  52 Ho 0.75 0.5 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  53 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 99.7 86 14 0.997  54 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 100.0 86 14 1.000  55 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 100.5 86 14 1.005  56 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 101.0 86 14 1.010  57 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 101.5 86 14 1.015  58 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 100 0 1.005  59 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 95 5 1.005  60 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 80 20 1.005  61 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 74 26 1.005  62 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 70 30 1.005 Dielectric Composition (mol %) Rare Earth Sample (Re₂O₃ Total Ba/ No. Element Content MgO Mn₂O₃ V₂O₅ Cr₂O₃ Content WO₃ Ba Ti Zr (TiZr)  63 Ho 0.75 0.2 0.02 — — 0.02 0.05 100.3 86 14 1.003  64 Ho 0.75 0.2 — 0.02 — 0.02 0.05 100.3 86 14 1.003  65 Ho 0.75 0.2 — — 0.02 0.02 0.05 100.3 86 14 1.003  66 Ho 0.75 0.2 0.03 — — 0.03 0.05 100.3 86 14 1.003  67 Ho 0.75 0.2 — 0.03 — 0.03 0.05 100.3 86 14 1.003  68 Ho 0.75 0.2 — — 0.03 0.03 0.05 100.3 86 14 1.003  69 Ho 0.75 0.2 0.01 0.02 — 0.03 0.05 100.3 86 14 1.003  70 Ho 0.75 0.2 0.05 0.02 — 0.07 0.05 100.3 86 14 1.003  71 Ho 0.75 0.2 0.05 — 0.2 0.25 0.05 100.3 86 14 1.003  72 Ho 0.75 0.2 0.05 0.01 0.2 0.26 0.05 100.3 86 14 1.003  73 Ho 0.75 0.2 0.05 0.05 0.2 0.3 0.05 100.3 86 14 1.003  74 Ho 0.75 0.2 0.2 0.2 0.2 0.6 0.05 100.3 86 14 1.003  75 Ho 0.75 0.2 0.6 — — 0.6 0.05 100.3 86 14 1.003  76 Ho 0.75 0.2 — 0.6 — 0.6 0.05 100.3 86 14 1.003  77 Ho 0.75 0.2 — — 0.6 0.6 0.05 100.3 86 14 1.003  78 Ho 0.75 0.2 0.7 — — 0.7 0.05 100.3 86 14 1.003  79 Ho 0.75 0.2 — 0.7 — 0.7 0.05 100.3 86 14 1.003  80 Ho 0.75 0.2 — — 0.7 0.7 0.05 100.3 86 14 1.003  81 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0 100.3 86 14 1.003  82 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.025 100.3 86 14 1.003  83 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.05 100.3 86 14 1.003  84 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.1 100.3 86 14 1.003  85 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.2 100.3 86 14 1.003  86 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.3 100.3 86 14 1.003  87 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.4 100.3 86 14 1.003  88 Ho 0.75 0.2 0.025 0.05 0.2 0.275 0.05 100.3 86 14 1.003  89 Ho 0.00 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  90 Ho 0.25 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  91 Ho 0.5 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 Dielectric Composition (mol %) Rare Earth Sample (Re₂O₃ Total Ba/ No. Element Content MgO Mn₂O₃ V₂O₅ Cr₂O₃ Content MoO₃ Ba Ti Zr (TiZr)  92 Ho 1.0 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  93 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  94 Ho 2.0 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  95 Ho 4.0 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  96 Sm 0.25 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  97 Sm 0.75 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  98 Eu 0.75 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003  99 Gd 0.75 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 100 Tb 0.75 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 101 Dy 0.75 0.3 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 102 Er 0.75 0.25 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 103 Tm 0.75 0.25 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 104 Yb 0.75 0.25 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 105 Yb 1.0 0.25 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 106 Y 1.0 0.25 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 107 Ho/ 0.5/ 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 Dy 0.5 108 Ho/ 0.5/ 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 Dy/ 0.5/ Yb 0.5 109 Sm/ 0.2/ 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 Ho/ 0.5/ Yb 0.1 110 Sm/ 0.5/ 0.2 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 Yb 1.0 111 Ho 0.75 0 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 112 Ho 0.75 0.1 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 113 Ho 0.75 0.4 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 114 Ho 0.75 0.5 0.15 0.05 0.2 0.4 0.05 100.3 86 14 1.003 115 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 99.7 86 14 0.997 116 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 100.0 86 14 1.000 117 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 100.5 86 14 1.007 118 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 101.0 86 14 1.010 119 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.05 101.5 86 14 1.015 120 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 100 0 1.005 121 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 95 5 1.005 122 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 80 20 1.005 123 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 74 26 1.005 124 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.05 100.5 70 30 1.005 Dielectric Composition (mol %) Addition Rare Earth amounts Sample (Re₂O₃ Total (MoO₃ + Ba/ No. Element Content MgO Mn₂O₃ V₂O₅ Cr₂O₃ Content WO₃) Ba Ti Zr (TiZr) 125 Ho 0.75 0.2 0.02 — — 0.02 0.025 + 100.3 86 14 1.003 0.03 126 Ho 0.75 0.2 — 0.02 — 0.02 0.025 + 100.3 86 14 1.003 0.03 127 Ho 0.75 0.2 — — 0.02 0.02 0.025 + 100.3 86 14 1.003 0.03 128 Ho 0.75 0.2 0.03 — — 0.03 0.025 + 100.3 86 14 1.003 0.03 129 Ho 0.75 0.2 — 0.03 — 0.03 0.025 + 100.3 86 14 1.003 0.03 130 Ho 0.75 0.2 — — 0.03 0.03 0.025 + 100.3 86 14 1.003 0.03 131 Ho 0.75 0.2 0.01 0.02 — 0.03 0.025 + 100.3 86 14 1.003 0.03 132 Ho 0.75 0.2 0.05 0.02 — 0.07 0.025 + 100.3 86 14 1.003 0.03 133 Ho 0.75 0.2 0.05 — 0.2 0.25 0.025 + 100.3 86 14 1.003 0.03 134 Ho 0.75 0.2 0.05 0.01 0.2 0.26 0.025 + 100.3 86 14 1.003 0.03 135 Ho 0.75 0.2 0.05 0.05 0.2 0.3 0.025 + 100.3 86 14 1.003 0.03 136 Ho 0.75 0.2 0.2 0.2 0.2 0.6 0.025 + 100.3 86 14 1.003 0.03 137 Ho 0.75 0.2 0.6 — — 0.6 0.025 + 100.3 86 14 1.003 0.03 138 Ho 0.75 0.2 — 0.6 — 0.6 0.025 + 100.3 86 14 1.003 0.03 139 Ho 0.75 0.2 — — 0.6 0.6 0.025 + 100.3 86 14 1.003 0.03 140 Ho 0.75 0.2 0.7 — — 0.7 0.025 + 100.3 86 14 1.003 0.03 141 Ho 0.75 0.2 — 0.7 — 0.7 0.025 + 100.3 86 14 1.003 0.03 142 Ho 0.75 0.2 — — 0.7 0.7 0.025 + 100.3 86 14 1.003 0.03 143 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0 100.3 86 14 1.003 144 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.013 + 100.3 86 14 1.003 0.01 145 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.025 + 100.3 86 14 1.003 0.03 146 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.025 + 100.3 86 14 1.003 0.05 147 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.1 + 100.3 86 14 1.003 0.1 148 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.15 + 100.3 86 14 1.003 0.15 149 Ho 0.75 0.2 0.05 0.1 0.1 0.25 0.2 + 100.3 86 14 1.003 0.2 150 Ho 0.75 0.2 0.025 0.05 0.2 0.275 0.025 + 100.3 86 14 1.003 0.03 151 Ho 0.00 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.03 152 Ho 0.25 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.03 153 Ho 0.5 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.03 154 Ho 1.0 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.03 155 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 156 Ho 2.0 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 157 Ho 4.0 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 158 Sm 0.25 0.3 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 159 Sm 0.75 0.3 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 160 Eu 0.75 0.3 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 161 Gd 0.75 0.3 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 162 Tb 0.75 0.3 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 163 Dy 0.75 0.3 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 164 Er 0.75 0.1 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 165 Tm 0.75 0.1 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 166 Yb 0.75 0.1 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 167 Yb 1.0 0.1 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 168 Y 1.0 0.1 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 169 Ho/ 0.5/ 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 Dy 0.5  0.025 170 Ho/ 0.5/ 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 Dy/ 0.5/ 0.025 Yb 0.5  171 Sm/ 0.2/ 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 Ho/ 0.5/ 0.025 Yb 0.1  172 Sm/ 0.5/ 0.2 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 Yb 1.0  0.025 173 Ho 0.75 0 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 174 Ho 0.75 0.1 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 175 Ho 0.75 0.4 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 176 Ho 0.75 0.5 0.15 0.05 0.2 0.4 0.025 + 100.3 86 14 1.003 0.025 177 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.025 + 99.7 86 14 0.997 0.025 178 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.025 + 100.0 86 14 1.000 0.025 179 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.025 + 100.5 86 14 1.005 0.025 180 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.025 + 101.0 86 14 1.010 0.025 181 Ho 0.75 0.2 0.15 0.05 0.2 0.4 0.025 + 101.5 86 14 1.015 0.025 182 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.025 + 100.5 100 0 1.005 0.025 183 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.025 + 100.5 95 5 1.005 0.025 184 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.025 + 100.5 80 20 1.005 0.025 185 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.025 + 100.5 74 26 1.005 0.025 186 Ho 1.5 0.2 0.15 0.05 0.2 0.4 0.025 + 100.5 70 30 1.005 0.025

Thereafter, the dried ceramic slurry was ground and then calcined in air at about 800° C. for 6 hours. The calcined slurry was then crushed by employing a wet method in a ball mill added with ethanol for about 6 hours. Next, the crushed ceramic slurry was dried by being heated at about 150° C. for 6 hours, thereby obtaining the powder of the calcined ceramic slurry.

In a following step, a dielectric ceramic slurry was obtained by mixing and grinding 1000 g (100 parts by weight) of the powder of the dielectric ceramic slurry, 15 wt % of an organic binder and 50 wt % of water in a ball mill, wherein the organic binder includes acrylic ester polymer, glycerin, and a solution of condensed phosphate.

Next, the dielectric slurry was subjected to a vacuum air separator to remove air bubbles therefrom and formed into a thin film coated on a polyester film by using a reverse roll coater. Thus produced ceramic thin film on the polyester film was heated and dried at about 100° C. and then diced to thereby obtain square ceramic green sheets having a thickness of about 5 μm and a size of about 10 cm×10 cm.

Meanwhile, 0.9 g of ethyl cellulose dissolved in 9.1 g of butyl carbitol and 10 g of Nickel powder having an average diameter of about 0.5 μm were loaded and stirred in a stirrer for 10 hours to form a conductive paste for use in forming internal electrodes of ceramic capacitors. Thereafter, the conductive paste was printed on the prepared ceramic green sheets to form conductive patterns thereon and then the printed conductive paste was dried.

Subsequently, ten ceramic green sheets having the conductive patterns thereon were stacked against each other with the conductive patterns facing upward, thereby forming a laminated body. Every two neighboring sheets were disposed in such a manner that the conductive patterns provided thereon were shifted by one half of a pattern size along the length direction. The laminated body also included one or more ceramic dummy sheets stacked against each of the uppermost and the lowermost ceramic green sheets having conductive patterns thereon, the ceramic dummy sheets representing ceramic green sheets without having conductive patterns thereon.

Next, the laminated body was pressed with a load of about 40 tons at about 50° C. along the stacking direction of the ceramic sheets in the laminated body. Afterwards, the pressed laminated body was diced into a multiplicity of chip shaped ceramic bodies having a size of about 3.2 mm×1.6 mm.

Thereafter, Ni external electrodes were formed at two opposite sides of each chip shaped ceramic body by, e.g., a dipping method, one end portion of each of the internal electrodes being exposed to one of the two opposite sides of each chip shaped ceramic body. Then, the chip shaped ceramic bodies were loaded into a furnace capable of controlling an atmosphere therein and the organic binder contained in the loaded ceramic bodies was removed by heating the furnace in an N₂ atmosphere. Then, the binder-removed chip shaped ceramic bodies were sintered at about 1200° C. in a non-oxidative atmosphere with oxygen partial pressure being in 10⁻⁵ to 10⁻⁸ atm order range. Thereafter, the sintered chip-shaped ceramic bodies were re-oxidized in an oxidative atmosphere to thereby obtain multilayer ceramic capacitors as shown in the Drawing, wherein reference numerals 10, 12 and 14 in the Drawing represent dielectric layers, internal electrodes and external electrodes, respectively.

Tables 2-1 to 2-6 exhibit a measurement result of electrical characteristics obtained from the thus produced multilayer ceramic capacitors, wherein a thickness of each dielectric layer incorporated in the capacitors was about 3 μm.

The electrical characteristics of the multilayer ceramic capacitors were obtained as follows.

(A) Relative permittivity or dielectric constant ε_(s) was computed based on a facing area of a pair of neighboring internal electrodes, a thickness of a dielectric layer positioned between the pair of neighboring internal electrodes, and the capacitance of a multilayer ceramic capacitor obtained under the condition of applying at 20° C. a voltage of 1.0 V (root mean square value) with a frequency of 1 kHz.

(B) Dielectric loss tan δ(%) was obtained under the same condition as established for measuring the permittivity cited above.

(C) resistivity (Ωcm) was acquired by measuring a resistance between a pair of external electrodes after DC 25 V was applied for 60 seconds at 20° C. The number following “E” in the notation of a resistivity value presented in the accompanying Tables 2-1 to 2-6 represents an order. For instance, 4.8E +12 represents 4.8×10¹².

(D) Accelerated life (second) was obtained by measuring time period until an insulation resistivity (ρ) becomes 1×10¹⁰ Ωcm in a DC electric field of 20 V/μm at 150° C.

(E) Capacitance variation ΔC/C₂₅ (%) was obtained by measuring capacitances at −55° C. and +125° C. in a thermostatic (or constant temperature) oven under the condition of applying a voltage of 1 V (rms value) with a frequency of 1 kHz, wherein C₂₅ represents a capacitance at 25 C. and ΔC represents the difference between C₂₅ and a capacitance measured at −55° C. or 125° C.

TABLE 2 Sinter- Capacitance ing Resistivity Variation Accel- Tem- (Ω cm) at Δc/c₂₅ (%) erated Sample perature Permit- Tan δ Room −55° 85° Life Number (° C.) tivity (%) Temperature C. C. (sec)  1 1200 17900 10.0 5.7E+12 −60 −70 112000  2 1200 18100 9.8 6.4E+12 −56 −71 149000  3 1200 17800 9.9 6.5E+12 −55 −68 98000  4 1200 17500 8.8 5.3E+12 −55 −71 220000  5 1200 17400 8.7 5.8E+12 −50 −70 231000  6 1200 17000 8.3 5.7E+12 −50 −70 241000  7 1200 15900 7.2 4.8E+12 −48 −72 270000  8 1200 14900 7.0 4.9E+12 −45 −71 269000  9 1200 15400 6.9 4.5E+12 −47 −71 277000  10 1200 12800 5.3 4.0E+12 −42 −72 302000  11 1200 13200 5.3 3.9E+12 −44 −73 318000  12 1200 13300 5.2 2.7E+12 −41 −73 322000  13 1200 11900 3.9 3.1E+12 −40 −74 358000  14 1200 10500 3.6 2.4E+12 −41 −75 389000  15 1200 11600 3.7 1.9E+12 −40 −74 379000  16 1200 9800 2.9 1.8E+12 −35 −76 514000  17 1200 9900 3.1 1.2E+12 −36 −78 530000  18 1200 9500 2.7 8.0E+11 −34 −77 548000  19 1200 15900 5.9 4.3E+12 −44 −71 158000  20 1200 16400 6.3 3.4E+12 −43 −71 218000  21 1200 16900 6.8 5.6E+12 −47 −72 275000  22 1200 17600 7.9 5.3E+12 −50 −74 318000  23 1200 18000 8.2 6.6E+12 −49 −75 329000  24 1200 18300 8.5 4.7E+12 −52 −76 376000  25 1200 1880 10.7 7.2E+12 −55 −81 479000  26 1200 14800 5.8 5.7E+12 −48 −73 297000  27 1200 18200 12.8 4.5E+12 −60 −68 157000  28 1200 17400 9.3 4.2E+12 −56 −70 218000  29 1200 16900 7.5 5.5E+12 −54 −72 238000  30 1200 14500 7.1 5.9E+12 −53 −72 364000  31 1200 12300 5.6 7.0E+12 −47 −73 497000  32 1200 9900 4.1 8.1E+12 −44 −74 663000  33 1200 Incapable of obtaining a sintered ceramic with high density  34 1200 17300 9.8 6.1E+12 −55 −73 207000  35 1200 14500 7.3 5.5E+12 −52 −73 221000  36 1200 14800 7.8 7.8E+12 −53 −74 228000  37 1200 12900 8.9 5.9E+12 −54 −75 248000  38 1200 13300 8.2 1.7E+12 −56 −72 215000  39 1200 12800 7.9 3.2E+12 −52 −73 273000  40 1200 14400 6.2 7.2E+12 −49 −73 210000  41 1200 14900 9.5 8.5E+12 −53 −75 238000  42 1200 11400 8.7 4.3E+12 −52 −76 247000  43 1200 15700 7.5 5.9E+12 −47 −72 229000  44 1200 18200 7.7 7.7E+12 −46 −73 255000  45 1200 16500 8.3 4.9E+12 −53 −74 218000  46 1200 14300 7.0 8.6E+12 −50 −73 279000  47 1200 12900 7.7 4.3E+12 −53 −72 285000  48 1200 15300 8.2 3.3E+11 −54 −73 289000  49 1200 19700 10.5 6.0E+12 −56 −69 254000  50 1200 18800 8.7 6.4E+12 −51 −74 233000  51 1200 13700 5.6 4.3E+12 −45 −77 221000  52 1200 9800 3.2 8.4E+12 −43 −82 196000  53 1200 Incapable of obtaining a sintered ceramic with high density  54 1200 11200 3.3 2.1E+12 −42 −73 418000  55 1200 14800 5.2 5.2E+12 −44 −72 348000  56 1200 17600 8.2 4.3E+12 −50 −70 221000  57 1200 19200 11.2 6.4E+12 −55 −67 63000  58 1200 9500 7.8 5.9E+12 −52 −71 327000  59 1200 11700 6.3 5.5E+12 −46 −73 346000  60 1200 14300 5.6 4.2E+12 −44 −75 374000  61 1200 12500 4.2 4.7E+12 −43 −73 412000  62 1200 9700 3.4 3.6E+12 −41 −71 447000  63 1200 17600 10.2 5.7E+12 −59 −71 132000  64 1200 18100 9.8 6.4E+12 −58 −72 134000  65 1200 17800 9.9 6.5E+12 −56 −76 127000  66 1200 17800 8.3 6.2E+12 −54 −73 213000  67 1200 17400 8.9 4.8E+12 −50 −72 221000  68 1200 17300 9.0 5.3E+12 −52 −72 209000  69 1200 15800 7.9 3.8E+12 −47 −73 296000  70 1200 15600 8.3 4.4E+12 −45 −72 285000  71 1200 14900 8.2 4.1E+12 −48 −73 281000  72 1200 12900 7.3 3.9E+12 −43 −75 329000  73 1200 13100 7.4 3.7E+12 −43 −72 354000  74 1200 13200 7.1 2.4E+12 −42 −75 312000  75 1200 10900 5.2 3.3E+12 −44 −73 489000  76 1200 11300 4.9 2.9E+12 −42 −74 463000  77 1200 10900 4.7 2.4E+12 −41 −73 475000  78 1200 9700 3.8 2.8E+12 −36 −75 558000  79 1200 9500 3.5 1.8E+12 −37 −74 512000  80 1200 9200 3.7 1.3E+12 −35 −73 568000  81 1200 14900 5.9 4.1E+12 −45 −72 164000  82 1200 16800 7.1 3.8E+12 −44 −69 238000  83 1200 17300 7.7 5.7E+12 −48 −75 218000  84 1200 17900 8.1 5.8E+12 −50 −74 241000  85 1200 18200 8.9 4.5E+12 −49 −72 318000  86 1200 18900 9.5 4.4E+12 −52 −76 367000  87 1200 19200 11.6 6.7E+12 −55 −81 428000  88 1200 14800 5.8 5.5E+12 −44 −72 295000  89 1200 18600 12.8 4.4E+12 −57 −69 168000  90 1200 18300 9.6 4.7E+12 −53 −71 206000  91 1200 17200 7.4 5.6E+12 −51 −71 226000  92 1200 16400 6.8 6.2E+12 −54 −75 263000  93 1200 13200 5.4 6.7E+12 −49 −72 437000  94 1200 9800 3.9 7.6E+12 −43 −73 554000  95 1200 Incapable of obtaining a sintered ceramic with high density  96 1200 18700 8.9 3.1E+12 −56 −74 208000  97 1200 15000 7.6 5.3E+12 −51 −72 243000  98 1200 14300 7.3 6.8E+12 −54 −75 243000  99 1200 13200 8.4 6.4E+12 −51 −73 222000 100 1200 12800 7.8 2.3E+12 −50 −75 273000 101 1200 12600 6.7 3.7E+12 −51 −71 264000 102 1200 14300 8.3 6.5E+12 −57 −73 243000 103 1200 13800 9.2 8.1E+12 −58 −71 245000 104 1200 12800 8.5 4.8E+12 −56 −73 231000 105 1200 14800 7.3 5.3E+12 −46 −75 251000 106 1200 16900 7.9 7.3E+12 −44 −74 233000 107 1200 15300 8.5 5.3E+12 −54 −78 239000 108 1200 14300 7.2 8.1E+11 −49 −78 242000 109 1200 12700 7.9 7.3E+12 −48 −74 264000 110 1200 14300 8.5 6.3E+12 −56 −74 274000 111 1200 18800 10.7 5.9E+12 −62 −67 278000 112 1200 17800 8.4 6.7E+12 −58 −70 229000 113 1200 14500 6.1 5.3E+12 −47 −77 253000 114 1200 8800 2.9 3.3E+12 −35 −84 201000 115 1200 Incapable of obtaining a sintered ceramic with high density 116 1200 12300 3.4 2.3E+12 −40 −79 396000 117 1200 15200 5.6 5.7E+12 −43 −74 374000 118 1200 16300 8.1 4.7E+12 −56 −67 238000 119 1200 18300 12.1 2.4E+12 −60 −78 89000 120 1200 9400 7.3 5.6E+12 −55 −73 318000 121 1200 12500 6.7 6.6E+12 −51 −72 335000 122 1200 13200 6.1 6.2E+12 −45 −73 359000 123 1200 11800 4.7 7.3E+12 −46 −75 422000 124 1200 9800 3.7 6.3E+12 −43 −74 439000 125 1200 18300 11.0 7.8E+12 −60 −73 154000 126 1200 18000 10.2 5.4E+12 −56 −73 143000 127 1200 17900 9.9 6.2E+12 −55 −76 147000 128 1200 17300 8.9 7.3E+12 −55 −77 208000 129 1200 17200 9.3 6.3E+12 −49 −74 219000 130 1200 16900 9.2 2.3E+12 −50 −70 226000 131 1200 15400 8.2 3.9E+12 −46 −74 320000 132 1200 15500 8.4 4.3E+12 −44 −72 332000 133 1200 14700 8.1 2.1E+12 −44 −74 312000 134 1200 13200 7.5 4.2E+12 −42 −74 398000 135 1200 13400 7.4 8.7E+12 −41 −74 400000 136 1200 13200 7.2 5.4E+12 −44 −76 394000 137 1200 11500 6.0 4.2E+12 −45 −74 478000 138 1200 12300 5.8 3.2E+12 −44 −74 495000 139 1200 10000 4.6 2.9E+12 −42 −74 454000 140 1200 9400 4.2 5.8E+12 −39 −78 576000 141 1200 9300 3.5 4.7E+12 −38 −77 548000 142 1200 9100 3.9 4.3E+12 −37 −74 579000 143 1200 3600 5.4 4.9E+12 −47 −73 163900 144 1200 17300 6.7 5.8E+12 −45 −70 247000 145 1200 16800 7.4 7.2E+12 −49 −72 264000 146 1200 16900 7.7 6.6E+12 −51 −70 277000 147 1200 16700 8.3 8.3E+12 −48 −74 296000 148 1200 19900 8.9 8.8E+12 −53 −76 352000 149 1200 18700 10.9 9.1E+12 −56 −80 448000 150 1200 15500 6.3 6.5E+12 −45 −73 277000 151 1200 17500 12.9 4.7E+12 −58 −70 209000 152 1200 19200 9.2 4.6E+12 −52 −69 218000 153 1200 17700 7.8 5.2E+12 −53 −70 234000 154 1200 16600 6.4 6.3E+12 −55 −78 289000 155 1200 14400 5.5 5.8E+12 −48 −75 398000 156 1200 9500 3.5 7.0E+12 −44 −74 493000 157 1200 Incapable of obtaining a sintered ceramic with high density 158 1200 18300 9.2 4.3E+12 −55 −73 212000 159 1200 15700 7.8 4.9E+12 −50 −70 231000 160 1200 15400 8.1 5.8E+12 −53 −74 253000 161 1200 13900 8.1 5.9E+12 −52 −75 247000 162 1200 13200 7.7 6.7E+12 −51 −73 254000 163 1200 12600 6.9 5.3E+12 −49 −74 253000 164 1200 14400 7.3 4.4E+12 −58 −75 243000 165 1200 13600 9.2 4.7E+12 −60 −70 251000 166 1200 12900 8.3 5.6E+12 −58 −71 249000 167 1200 14100 8.0 6.2E+12 −47 −74 244000 168 1200 15500 7.7 7.3E+12 −43 −72 212000 169 1200 14800 8.4 6.3E+12 −55 −75 246000 170 1200 14300 7.6 2.3E+12 −50 −76 247000 171 1200 13300 7.9 3.9E+12 −47 −76 252000 172 1200 14500 8.3 6.3E+11 −56 −74 263000 173 1200 18400 11.0 5.9E+12 −60 −70 269000 174 1200 17900 8.6 3.7E+12 −59 −69 237000 175 1200 14700 6.7 2.4E+12 −48 −76 246000 176 1200 8900 3.1 3.3E+12 −40 −82 196000 177 1200 Incapable of obtaining a sintered ceramic with high density 178 1200 13100 3.3 2.9E+12 −39 −76 374000 179 1200 14800 5.9 2.4E+12 −45 −76 348000 180 1200 16600 8.8 4.1E+12 −53 −66 243000 181 1200 17900 11.5 3.3E+12 −59 −74 91000 182 1200 9300 8.8 2.3E+12 −56 −72 363000 183 1200 13200 8.2 5.2E+12 −52 −73 382000 184 1200 14600 7.5 3.9E+12 −47 −72 402000 185 1200 12200 6.4 5.8E+12 −47 −77 432000 186 1200 9000 4.9 5.9E+12 −44 −75 453000

As clearly seen from Tables 1-1 to 1-7 and Tables 2-1 to 2-6, multilayer ceramic capacitors with highly improved reliability having relative permittivity ε_(s) equal to or greater than 10,000, capacitance variation ΔC/C₂₅ within the range from −80% to +30% at temperatures ranging from −55° C. to +125° C., tan δ of 10.0% or less and accelerated life of 200,000 seconds or greater could be obtained from the above samples sintered in a non-oxidative atmosphere even at a temperature of 1200° C. or lower in accordance with the present invention.

However, samples 1 to 3, 16 to 19, 25, 27, 32, 33, 49, 52, 53, 57, 58, 62 to 65, 78 to 87, 89, 94, 95, 111, 114, 115, 119, 120, 124 to 127, 140 to 143, 149, 151, 156, 157, 173, 176, 177, 181, 182, 186 (marked with “” at the column of sample numbers in Tables) could not satisfy the above-specified electrical characteristics. Therefore, it appears that such samples fall outside a preferable compositional range of the present invention.

The reasons why the preferable compositional range for the dielectric ceramics in accordance with the present invention should be limited to certain values will now be described.

First, when the content of an oxide of a rare-earth element represented by Re is 0 mol part in terms of Re₂O₃ (i.e., assuming the oxide of Re is in the form of Re₂O₃) as in the samples 27, 89 and 151, the tan δ thereof goes over 10.0%; whereas when the oxide of Re is set to be 0.25 mol part in terms of Re₂O₃ as in samples 28, 90 and 152, the desired electrical characteristics can be successfully obtained.

Further, when the content of the oxide of the rare-earth element Re is 2.0 mol part in terms of Re₂O₃ as in the samples 32, 94 and 156, the dielectric constant of the produced multilayer ceramic capacitors may become equal to or less than 10,000. However, when the content of the oxide of Re is set to be 1.5 mol part in terms of Re₂O₃ as in the samples 31, 93 and 155, the desired electrical characteristics can be successfully obtained.

Accordingly, the preferable range of the content of oxide of the rare-earth element Re is from 0.25 to 1.5 mol part in terms of Re₂O₃.

It is noted that same effects can be produced regardless of whether a single rare-earth element is used or two or more of rare-earth elements are used together as long as the above-described preferable content range of the rare-earth element Re is satisfied.

When the content of an oxide of Mg is 0 mol part in terms of MgO as in the samples 49, 111 and 173, the tan δ goes over 10.0%; whereas when the oxide of Mg is set to be 0.1 mol part in terms of MgO as in samples 50, 112 and 174, the desired electrical characteristics can be successfully obtained.

In addition, when the content of the oxide of Mg is 0.5 mol part in terms of MgO as in the samples 52, 114, 176, the relative permittivity of the produced multilayer ceramic capacitors may become equal to or less than 10,000 and the capacitance variation ΔC/C₂₅ of the produced multilayer ceramic capacitors may deviate from the range from −80% to +30% when the temperature varies from −55° C. to +125° C.; and accordingly, the desired accelerated life cannot be obtained. However, when the content of the oxide of Mg is set to be 0.4 mol part in terms of MgO as in samples 51, 113 and 175, the desired electrical characteristics can be successfully obtained.

Accordingly, the content of the oxide of Mg desirably ranges from 0.1 to 0.4 mol part in terms of MgO.

When the content of an oxide of each element Mn, V or Cr is 0.02 mol part in terms of Mn₂O₃, V₂O₅ or Cr₂O₃, as in the samples 1 to 3, 63 to 65 and 125 to 127, the tan δ thereof goes over 10.0% or the desired accelerated life of the produced multilayer ceramic capacitors may not be obtained; whereas when the total content of the oxides of Mn, V and Cr is set to be 0.03 mol part in terms of Mn₂O₃, V₂O₅ and Cr₂O₃, as in the samples 4 to 7, 66 to 68 and 128 and 130, the desired characteristics can be successfully attained.

Further, when the content of an oxide of Mn, V or Cr is 0.7 mol part in terms of Mn₂O₃, V₂O₅ or Cr₂O₃, as in the samples 16 to 18, 78 to 80 and 140 and 142, the dielectric constant of the capacitors becomes equal to or less than 10,000. However, when the content of sum of the oxides of Mn, V and Cr is set to be 0.6 mol part in terms of Mn₂O₃, V₂O₅ and Cr₂O₃, as in samples 12 to 15, 75 to 77 and 137 to 139, the desired characteristics can be successfully attained.

Accordingly, it is preferable that the total amount of oxides of Mn, V and Cr ranges from 0.03 to 0.6 mol part in terms of Mn₂O₃, V₂O₅ and Cr₂O₃.

Further, it is to be noted that same effects can be obtained regardless of whether an oxide of one of the elements Mn, V and Cr is used alone or two or more thereof are used together as in samples 4 to 15, 66 to 77 and 128 to 139 as long as the total content thereof satisfies the above specified range.

Further, when the content of oxides of Mo and W is greater than 0.4 mol part in terms of MoO₃ and WO₃ as in the samples 25, 87 and 149, the tan δ thereof may be deteriorated over 10.0% and the capacitance variation ΔC/C₂₅ exceeds the range from −80% to +30% with the temperature varying from −55° C. to +125° C. However, when the total content of oxides is set to be 0.3 mol part as in samples 24, 86 and 148, the desired electrical characteristics can be successfully obtained.

Accordingly, it is preferable that the total content of the oxides of Mo and W ranges from 0 to 0.3 mol part in terms of MoO₃ and WO₃.

Furthermore, same effects can be obtained regardless of whether the oxides of Mo and W are used separately as in samples 20 to 24 and 82 to 86 or used together as in samples 144 to 148.

When the ratio Ba/(Ti_(1−x)Zr_(x)) is 0.997 as in the samples 53, 115 and 177, a highly densified ceramic body may not be obtained by the sintering at 1200° C.; whereas when the ratio Ba/(Ti_(1−x)Zr_(x)) is 1.000 as in the samples 54, 116 and 178, the desired electrical characteristics can be successfully obtained.

Further, when the ratio Ba/(Ti_(1−x)Zr_(x)) is 1.015 as in the samples 57, 119 and 181, the tan δ thereof may be deteriorated over 10.0% or the desired electrical characteristics can not be obtained; whereas when the ratio Ba/(Ti_(1−x)Zr_(x)) is 1.010 as in the samples 56, 118 and 180, the desired electrical characteristics can be successfully obtained. Accordingly, the optimum range of the ratio Ba/(Ti_(1−x)Zr_(x)) ranges from about 1.000 to about 1.010.

Ca or Sr can be used instead of Ba for adjusting the ratio Ba/(Ti_(1−x)Zr_(x)). That is, as long as the ratio of the sum of Ba, Ca and Sr to (Ti_(1−x)Zr_(x)). i.e., (Ba+Ca)/(Ti_(1−x)Zr_(x)) ratio, (Ba+Sr)/(Ti_(1−x)Zr_(x)) ratio or (Ba+Ca+Sr)/(Ti_(1−x)Zr_(x)) satisfies the optimum range from 1.000 to 1.010, the desired characteristics can be obtained.

Still further, barium carbonate, barium acetate, barium nitrate, calcium acetate, strontium nitrate or the like can be used in controlling the ratios mentioned above.

Although the present invention has been described with reference to the multilayer ceramic capacitors in this specification, it will be apparent to those skilled in the art that the present invention is also applicable to a single layer ceramic capacitor.

When x is 0 in Ti_(1−x)Zr_(x) as in the samples 58, 120 and 182, the dielectric constant ε_(s) becomes equal to or less than 10,000, whereas when x is 0.26 as in the samples 61, 123 and 185, the desired electrical characteristics can be obtained. Accordingly, the optimum range of x in Ti_(1−x)Zr_(x) ranges about 0.05 to 0.26.

The present invention can produce a multilayer ceramic capacitor capable of providing a desired operating life with a highly improved reliability, wherein the capacitor exhibits a relative permittivity ε_(s) of 10,000 or greater, tan δ of 10.0% or less and a capacitance variation ΔC/C₂₅ ranging from −80% to +30% within the temperature range from −55° C. to +125° C. In accordance with the present invention, there is provided a multilayer ceramic capacitor capable of providing a desired operating life with a highly improved reliability when the dielectric ceramic composition includes one or more oxides selected from the group consisting of oxides of Mo and W, the contents of the oxides being included therein in amounts ranging about 0.025 to 0.3 mol part by assuming that the oxides of Mo and W are MoO₃ and WO₃, respectively.

While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. 

What is claimed is:
 1. A dielectric ceramic composition comprising: 100 mol part of an oxide of Ba, Ti and Zr, the content of the oxide of the Ba, Ti and Zr being calculated by assuming that the oxide thereof is Ba(Ti_(1−x)Zr_(x))O₃; 0.25 to 1.5 mol part of an oxide of Re, Re representing one or more elements selected from the group consisting of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Y, the content of the oxide of the Re being calculated by assuming that the oxide thereof is Re₂O₃; 0.1 to 0.4 mol part of an oxide of Mg, the content of the oxide of the Mg being calculated by assuming that the oxide thereof is MgO; and 0.03 to 0.6 mol part of oxides of one or more elements selected from the group consisting of Mn, V and Cr, the contents of the oxides of the Mn, V and Cr being calculated by assuming that the oxides thereof are Mn₂O₃, V₂O₅ and Cr₂O₃, respectively, wherein a ratio of Ba/(Ti_(1−x)Zr_(x)) ranges from about 1.000 to about 1.010 and x in Ti_(1−x)Zr_(x) ranges from about 0.05 to about 0.26.
 2. The dielectric ceramic composition of claim 1, wherein the dielectric ceramic composition further comprises one or more oxides selected from the group consisting of an oxide of Mo and an oxide of W, the contents of the oxides of Mo and W being calculated by assuming that the oxides of Mo and W are MoO₃ and WO₃, respectively and each of the contents of the oxides of Mo and W ranging about 0.025 to 0.3 mol part.
 3. A ceramic capacitor comprising: one or more ceramic dielectric layers, each of the ceramic dielectric layers including a dielectric ceramic composition of claim 1; and two or more internal electrodes, a dielectric layer being disposed between adjacent two internal electrodes.
 4. The ceramic capacitor of claim 3, wherein the dielectric ceramic composition further comprises one or more oxides selected from the group consisting of an oxide of Mo and an oxide of W, the contents of the oxides of Mo and W being calculated by assuming that the oxides of Mo and W are MoO₃ and WO₃, respectively and each of the contents of the oxides of Mo and W ranging about 0.025 to 0.3 mol part. 